Injection molding apparatus having a nozzle sleeve

ABSTRACT

An injection molding apparatus that includes a hot runner and a mold. The hot runner includes at least one nozzle that engages a nozzle-receiving cavity of the mold. The molding apparatus further includes a nozzle sleeve surrounding a portion of the nozzle and having a nozzle-sealing opening that receives the nozzle. The nozzle sleeve is movably secured to the hot runner or the mold so that when the mold is removed from the hot runner, the nozzle sleeve remains secured to the corresponding part of the apparatus. When the mold and hot runner are engaged with one another, the nozzle sleeve is springingly urged into sealing engagement with a sealing surface of the nozzle receiving cavity of the mold.

TECHNICAL FIELD OF THE INVENTION

The present disclosure generally relates to the field of injectionmolding. In particular, the present disclosure is directed to a nozzlesleeve for an injection molding apparatus.

DESCRIPTION OF THE RELATED ART

Injection molding of items made of plastic and other molding materialsoften utilizes a multi-nozzle hot-runner assembly that removably engagesa corresponding mold assembly to distribute the molding material eitherto differing locations of a single mold cavity or to differing moldcavities, depending on the item(s) being molded. Such a hot-runnerassembly typically includes a manifold that distributes the moldingmaterial to multiple nozzles that deliver the molding material to themold. Each nozzle typically extends from the manifold into anozzle-receiving cavity of the mold assembly that, in turn, is in fluidcommunication with the corresponding mold cavity. In order to inhibitmolding material from flowing around the nozzles and out of thenozzle-receiving cavities of the mold assemblies, a sealing arrangementis provided between each nozzle and the nozzle-receiving cavity.

Two typical sealing arrangements for inhibiting the molding materialfrom flowing out of the nozzle-receiving cavities utilize thermalexpansion of the nozzles and the mold assembly to create a compressionseal between each nozzle and the sidewall of the correspondingrespective nozzle-receiving cavity. In one of these arrangements thecompression seal is formed between the tip of the nozzle and thesidewall of the nozzle-receiving cavity, and in the other arrangementthe compression seal is formed between the housing of the nozzle and thesidewall of the nozzle-receiving cavity. When the hot runner and moldassemblies are at room temperature, the nozzles and nozzle-receivingcavities are sized to allow the nozzles to move freely, though withrelatively tight clearances between the sealing surfaces, within thenozzle-receiving cavities. As the assemblies are preheated for use, thethermal expansion of the nozzles and mold assemblies causes the sealingsurfaces to contact one another and then press against one another toform a tight seal.

While these sealing arrangements function very well when the sealingsurfaces are properly finished, unworn and undamaged, theireffectiveness can be significantly diminished when either or both of thesealing surfaces become worn or damaged, e.g., from scratches, gouges,indentations, etc. Wearing/damaging of the sealing surfaces does nottypically occur when the mold assembly is engaged or disengaged with thehot runner assembly at room temperature. However, the sealing surfacescan, and often do, become worn/damaged when the mold assembly isdisengaged from and/or engage with the hot runner assembly when theassemblies are hot and, therefore, when the sealing surfaces are intight contact with each other or the outside diameter of the nozzle tipor housing is slightly larger than the inside diameter of the portion ofthe nozzle-receiving cavity at which the seal is normally formed.Reasons for disengaging and reengaging the mold assembly while theassemblies are still hot include changing the mold assembly, removingun-melted blockage and removing a color bubble when changing the colorof the molding material.

SUMMARY OF THE DISCLOSURE

In one aspect, the present disclosure is directed to an injectionmolding assembly. The injection molding assembly comprises a hot runnerthat includes an injection nozzle comprising a tip and having an outerperiphery. A mold is secured to the hot runner and includes a moldcavity and a nozzle-receiving cavity in fluid communication with themold cavity and receiving a portion of the injection nozzle. Thenozzle-receiving cavity includes a sealing surface and a tip regionreceiving the tip of the injection nozzle. A nozzle sleeve surrounds theouter periphery of at least a portion of the injection nozzle and issecured to the injection molding assembly independently of the injectionnozzle. The nozzle sleeve includes a nozzle sealing opening receiving aportion of the injection nozzle therethrough and is configured to form aseal with the injection nozzle at least when the injection nozzle andthe nozzle sleeve are at an operating temperature. The nozzle sleeve isspringingly urged between the hot runner and the sealing surface so asto seal the tip region relative to the nozzle-receiving cavity.

In another embodiment, the present disclosure is directed to a nozzlesleeve for surrounding a portion of an injection nozzle of a hot runnerand extending at least partially into a nozzle-receiving cavity of amold when the mold is engaged with the hot runner, wherein one of 1) thehot runner and 2) the mold includes a retainer for movingly retainingthe nozzle sleeve. The nozzle sleeve comprises a body having alongitudinal central axis and includes a nozzle-sealing opening forsealingly engaging the injection nozzle during molding. The body alsoincludes a cavity-sealing region for sealingly engaging thenozzle-receiving cavity of the mold during molding. The body furtherincludes a stop configured for engaging the retainer when the mold isdisengaged from the hot runner and when the nozzle sleeve is secured tothe one of 1) the hot runner and 2) the mold. The stop is alsoconfigured for being spaced from the retainer during molding.

In a further embodiment, the present disclosure is directed to a hotrunner for use with a mold having a nozzle-sleeve receiver. The hotrunner comprises a mold-confronting face for confronting the mold and atleast one nozzle proximate the mold-confronting face for delivering amolding material to the mold. A nozzle sleeve surrounds at least aportion of the at least one nozzle and includes a nozzle-sealing openingreceiving the at least one nozzle. The hot runner further comprises anozzle-sleeve retainer movably securing the nozzle sleeve to the hotrunner. The nozzle sleeve is springingly biased into engagement with thenozzle-sleeve retainer when the mold is distal from the hot runner, andthe nozzle sleeve is springingly biased into sealing engagement with thenozzle-sleeve receiver when the mold is properly engaged with the hotrunner.

In yet another embodiment, the present disclosure is directed to aninjection mold for use with a hot runner that has a mold-confrontingface and includes at least one nozzle proximate the mold-confrontingface. The injection mold comprises and nozzle-sleeve receiver and anozzle sleeve including a nozzle-sealing opening for receiving the atleast one nozzle when the hot runner is properly engaged with theinjection mold. The injection mold also comprises a nozzle-sleeveretainer movably securing the nozzle sleeve to the injection mold. Thenozzle sleeve is springingly biased into engagement with thenozzle-sleeve retainer when the injection mold is distal from the hotrunner, and the nozzle sleeve is springingly biased into sealingengagement with the nozzle-sleeve receiver when the mold is properlyengaged with the hot runner.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a partial cross-sectional view/partial elevational view of amolding apparatus made in accordance with the present invention;

FIG. 2 is an enlarged partial cross-sectional view of the moldingapparatus of FIG. 1 showing one of the nozzle sleeves compressed betweenthe hot runner and mold portions of the apparatus during use thereof;

FIG. 3 is an enlarged partial cross-sectional view of the hot runner ofthe molding apparatus of FIG. 1 showing the nozzle sleeve of FIG. 2 whenthe mold is removed from the hot runner;

FIG. 4 is a partial cross-sectional view of an alternative moldingapparatus made in accordance with the present invention showing a nozzlesleeve secured to a hot-runner portion of the apparatus and compressedbetween the hot-runner portion and a mold portion of the apparatusduring use thereof;

FIG. 5 is a partial cross-sectional view of yet another alternativemolding apparatus made in accordance with the present invention showinga nozzle sleeve secured to a mold portion of the apparatus andcompressed between a hot-runner portion and the mold portion of theapparatus during use thereof; and

FIG. 6 is a partial cross-sectional view of the mold portion of themolding apparatus of FIG. 5 showing the nozzle sleeve when the moldportion is not engaged to the hot runner portion.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 illustrates a molding apparatus100 made in accordance with the present invention. As those skilled inthe art will readily appreciate, molding apparatus 100 may be adaptedfor any sort of injection molding process, including plastic injectionmolding processes, metal injection molding processes and compositeinjection molding processes, e.g., molding processes that utilize fillermaterials co-injected with a binder, among others. At a high level,molding apparatus 100 includes a hot runner 104 and a mold 108 engagedwith the hot runner. Hot runner 104 includes at least one injectionnozzle 112 that injects the relevant flowable material (not shown),e.g., molten plastic, molten metal, molten binder/filler mixture, etc.,into one or more mold cavities 116 formed within mold 108.

As discussed in the background section above, a problem that can ariseduring use of certain molding apparatuses is that the nozzle can bedamaged by the mold, particularly when the mold is disengaged from thehot runner when the apparatus has not sufficiently cooled. Moldingapparatus 100, however, includes a unique nozzle sleeve 120 for eachinjection nozzle 112 that substantially mitigates this problem. Asdiscussed below in connection with FIGS. 2 and 3, each nozzle sleeve 120inhibits the corresponding injection nozzle 112 from being damaged whenmold 108 is removed from hot runner 104 even when molding apparatus 100is hot by providing an intermediate structure between the injectionnozzle and the mold so that the injection nozzle is never in directcontact with the mold. Since there is never direct contact between eachnozzle 112 and mold 108 at any point during molding and when engaging ordisengaging the mold from hot runner 104, there is essentially noopportunity for the mold to damage that injection nozzle. Prior todescribing nozzle sleeve 120 and several variants thereof in detail,other components of molding assembly 100 will first be described.

Each injection nozzle 112 may be of any gate type, such as a valve-gatetype (not shown) or the thermal-gate type shown. In addition to the atleast one injection nozzle 112, hot runner 104 may include a manifold124 that delivers the molding material (not shown) to each of thenozzles. In accordance with conventional hot runner design, manifold 124may be located within a manifold cavity 128, which may be formed withina manifold plate 132 as shown, or alternatively may be formed within abuilt-up structure, e.g., a “front” plate (not shown) that wouldconfront mold 108 and one or more side closures (not shown) that wouldenclose the lateral sides of manifold 124. Those skilled in the art willunderstand the variety of ways to support a hot-runner manifold, such asmanifold 120, such that each of these ways need not be described orillustrated for those skilled in the art to appreciate the broadapplicability of the present disclosure. Hot runner 104 may also includea backing plate 136 that, among other things, closes manifold cavity128. An inlet 140 may also be provided for mating with an injectionmachine (not shown) that forces a molding material through passagewayswithin manifold 124 and each injection nozzle 112. Fasteners and othercomponents of hot runner 104, such as manifold heaters, coolingchannels, etc., are not shown for convenience.

Mold 108 may include, among other things, a cavity plate 144 and atleast one insert 148 that define the one or more mold cavities 116 thatdefine the part(s) to be molded. Mold 108 may be secured to hot runner104 using any suitable means (not shown) such as fasteners. Other partsthat mold 108 may include, such as an insert plate, ejector componentsfor ejecting the molded part(s) from the mold, alignment pins, coolingchannels, etc., are not shown for convenience. Of course, those skilledin the art will readily understand how these and other components may beimplemented in mold 108 or any other mold compatible with the presentinvention. In this example and as discussed in more detail belowrelative to FIG. 2, cavity plate 144 may include a nozzle-receivingcavity 152 that receives a corresponding injection nozzle of hot runner104, as well as receives the corresponding nozzle sleeve 120. Thoseskilled in the art will readily appreciate that hot runner 104 and mold108 shown and described and the alternative embodiments thereofdescribed above are merely exemplary and should not be construed aslimiting the scope of the present invention.

FIGS. 2 and 3 more particularly illustrate the arrangement of nozzlesleeve 120 within molding apparatus 100 of FIG. 1. Referring to FIGS. 2and 3, nozzle sleeve 120 is generally tubular in shape along the centrallongitudinal axis 156 of injection nozzle 112 so as to surround aportion of the nozzle. Nozzle sleeve 120 includes a nozzle sealingopening 160 configured to form a tight seal with injection nozzle 112 atleast when mold assembly is at operating temperature. This seal may bereferred to as the “nozzle seal.” In the embodiment shown, the nozzleseal provided by sealing opening 160 is effected by a tight fit betweenthe sides of the opening and injection nozzle 112 caused by thermalexpansion of the parts during their heating to operating temperature. Inalternative embodiments, the nozzle seal may be provided by other means,such as an O-ring (not shown) made of a suitable material or aninterference fit between a flexible portion (not shown) of nozzle sleeve120 that contacts injection nozzle 112 entirely around its outerperiphery and flexes so as to create the nozzle seal (see, e.g., FIGS. 5and 6, wherein integral spring 524 creates such a seal with nozzle 544).In whatever manner the nozzle seal is formed between nozzle sleeve 120and injection nozzle 112, it must be sufficient to inhibit the flow ofmolding material (not shown) into the space 164 between injection nozzle112 and nozzle sleeve 120 beyond the nozzle seal.

As best seen by comparing FIG. 3 to FIG. 2, nozzle sleeve 120 is springloaded so as to be movable between a disengaged position (FIG. 3),wherein the sleeve remains with hot runner 104 when mold 108 is removed,and an engaged position (FIG. 2), wherein the sleeve is urged against asealing surface 168 of nozzle-receiving cavity 152 so as to create aneffective cavity seal between the sleeve and cavity plate 144. Toaccommodate this movable configuration, nozzle sleeve 120 may be movablysecured to hot runner 104, e.g., by providing the hot runner with aretainer 172 that is engageable with one or more corresponding stops 174on the sleeve. In the embodiment shown, hot runner 104 is provided witha sleeve cavity 178 that slidably receives a flanged portion 182 ofnozzle sleeve 120. Correspondingly, with flanged portion 182 containingstop 174, retainer 172 may be the retainer ring shown that engages acorresponding groove 184 in the wall of sleeve cavity 178. Inalternative embodiments, retainer 172 and stop 174 may be otherstructures.

For example, if hot runner 104 is provided with a sleeve cavity similarto sleeve cavity 178 and nozzle sleeve 120 has a flanged portion similarto flanged portion 182, the retainer may be an annular plate (not shown)fastened to the front face 186 (FIG. 3) of the hot runner. In itsdisengaged position (similar to FIG. 3), the one or more stops 174 onthe flanged portion could be spring-urged into engagement with theannular plate. In yet other alternative embodiments wherein no sleevecavity is provided to hot runner 104, but nozzle sleeve 120 has aflanged portion similar to flanged portion 182, the retainer may be agenerally cup-shaped escutcheon (not shown) secured to front face 186 ofhot runner 104 that has a central opening smaller than the outsidediameter of the flanged portion but large enough to allow the rest ofthe nozzle sleeve to extend therethrough. In its disengaged position(similar to FIG. 3), the one or more stops 174 on the flanged portioncould be spring-urged into engagement with the escutcheon. Those skilledin the art will readily appreciate the wide variety of structures thatcan be used for retainer 172 and stop(s) 174.

Nozzle sleeve 120 may be spring-loaded using any of a variety of urgingmeans 188, such as the Belleville washer shown. Other urging meansinclude, but are not limited to, coil springs, leaf springs, torsionsprings, bellows springs, cantilever springs, resilient masses, andcombinations thereof. Urging means 188 may be formed separately fromnozzle sleeve 120 or integrally therewith. Regarding the latter, FIG. 4shows an integrally formed urging mean 428 for a nozzle sleeve 404movably secured to a hot runner 408. FIGS. 5 and 6 show an integrallyformed urging means 524 for a nozzle sleeve 504 movably secured to amold 508. Those skilled in the art will readily recognize how toimplement the urging means selected for a particular application.Referring again to FIGS. 2 and 3, the urging power of urging means 188may be selected so that the urging means can move nozzle sleeve 120against the friction of the nozzle seal when at operating temperature orbelow or, alternatively, at or below another temperature lower than theoperating temperature, depending upon the criteria for a particulardesign. Nozzle sleeve 120 may be made of any suitable material such as420SS, H13, etc. Of course, other materials may be used.

FIG. 4 illustrates an alternative molding apparatus 400 that includes atleast one nozzle sleeve 404 movably secured to a hot runner 408 andinserted into a nozzle-receiving cavity 412 of a mold 416. Nozzle sleeve404 is similar to nozzle sleeve 120 of FIGS. 1-3 in terms of its beingsecured to hot runner 408, its sealing relationship to nozzle 420 andits being spring-loaded into sealing engagement with mold 416 when themold is secured to the hot runner and into engagement with retainers 424when the mold is not present. That said, nozzle sleeve 404, hot runner408 and mold 416 have some differences relative to the correspondingrespective components of hot runner assembly 100 of FIGS. 1-3. Moreparticularly, one difference is that nozzle sleeve 404 of FIG. 4 has anintegrally formed urging means 428. In this example, urging means 428comprises a relatively thin outwardly and upwardly extending integralflange integral with nozzle sleeve 404. This integral flange may belikened to a Belleville washer fixedly secured to nozzle sleeve 404 atthe inner periphery of washer and may be made, e.g., by a moldingprocess or by milling. Urging means 428 may work in substantially thesame manner as the Belleville washer Urging means 188 of FIGS. 1-3.

Another difference between the embodiment of FIG. 4 and the embodimentof FIGS. 1-3 is that nozzle sleeve 404 of FIG. 4 is secured to hotrunner 408 using a plurality of washer-type retainers 424, which may besecured to the hot runner using any suitable means, such as the screws432 shown. Retainers 424 may be any suitable shape, and each may engagea corresponding recess 436 within nozzle sleeve 404, if desired. Ifneeded, the shape of each recess 436 may be made to conformally engagethe corresponding retainer 424 so as to inhibit rotation of nozzlesleeve 404 about its central longitudinal axis 440.

Yet another difference between the embodiment of FIG. 4 and theembodiment of FIGS. 1-3 is that nozzle-receiving cavity 444 of mold 416has a tapered section 448 that provides not only a tapered sealingsurface 452 if a face-to-face seal is desired, but also a self-alignmentmeans for ensuring that nozzle sleeve 404 and nozzle 420 are properlyaligned with the sprue opening 456 into the mold cavity 460. Any one ormore of these differing features may be used in any particular nozzlesleeve as desired to suit a particular design.

FIGS. 5 and 6 illustrate yet another embodiment of a molding apparatus500 made in accordance with the present invention. Unlike moldingapparatuses 100 and 400 of FIGS. 1-3 and 4, respectively, that each havea nozzle sleeve 120, 404 secured to a hot runner 104, 408, moldingapparatus 500 of FIGS. 5 and 6 has a nozzle sleeve 504 secured to themold 508, rather than the hot runner 512. As with nozzle sleeves 120,404 discussed above, nozzle sleeve 504 may be secured to mold 508 in anysuitable manner, such as the ring-type retainer 516 shown. Asillustrated in FIG. 6, nozzle sleeve 504 includes one or more stops 520that are springingly urged into engagement with retainer 516 when hotrunner 512 (FIG. 5) is not present or is otherwise moved away from mold508. Nozzle sleeve 504 may be urged into engagement with retainer 516using any suitable urging means, such as an integral urging means shownand described above in connection with FIGS. 1-4, e.g., acantilever-type spring as shown in FIG. 4 or a non-integral urgingmeans, e.g., the Belleville washer spring of FIGS. 1-3. In theembodiment shown in FIGS. 5-6, the urging means is an integral spring524 formed in a portion of nozzle sleeve 504 that allows that portion ofthe nozzle sleeve to flex. This flexing is best seen by comparing FIG.6, wherein: 1) a generally toroidally shaped (in three dimensions) tip528 is engaged with frusto-conical nozzle-sleeve-engaging surface 532 ofnozzle-receiving cavity 536 near the upper end (relative to FIG. 6); 2)integral spring 524 has a relatively steep slope; and 3) nozzle-sealingopening 540 is larger than the outside diameter of nozzle 544, to FIG.5, wherein: 1) tip 528 is much lower on nozzle-sleeve-engaging surface532; 2) integral spring 524 has a shallower slope; and 3) tip 528 iscompressed so that nozzle-seal opening 540 seals tightly against nozzle544.

As can be readily imagined for the transition between the state of FIG.6 to the state of FIG. 5, as hot runner 512 (FIG. 5) presses down onnozzle sleeve 504, which initially projects above the surface 548 ofmold 508 that confronts the hot runner as in FIG. 6, toroidally shapedtip 528 slides along tapered-sleeve-engaging surface 532, therebycausing integral spring 524 to flex to allow further movement of thesleeve and causing the tip to compress so as to tightly engage nozzle544. It is noted that the amount of travel of nozzle sleeve 504, theamount of flexure of integral spring 524 and the extent of compressionof toroidally shaped tip 528 are exaggerated in FIGS. 5 and 6 for thesake of illustration. However, those skilled in the art will readilyappreciate that the seals affected by nozzle sleeve 504 of FIGS. 5 and 6when hot runner 512 is fully engaged with mold 508 can be substantiallythe same as the seals affected by each of nozzle sleeve 120 of FIGS. 1-3and nozzle sleeve 404 of FIG. 4. That is, nozzle sleeve 504 of FIGS. 5and 6 provides a nozzle seal with nozzle 544 and a cavity seal withnozzle-receiving cavity 536. As can be readily seen in FIG. 6, whennozzle sleeve 504 is urged into engagement with retainer 516,nozzle-sealing opening 540 is larger than the outside circumference ofnozzle 544 so that when hot runner 512 is moved away from mold 508, thenozzle can move freely out of the nozzle-seal opening and the rest ofthe nozzle sleeve.

Exemplary embodiments have been disclosed above and illustrated in theaccompanying drawings. It will be understood by those skilled in the artthat various changes, omissions and additions may be made to that whichis specifically disclosed herein without departing from the spirit andscope of the present invention.

1. An injection molding assembly, comprising: a hot runner that includes an injection nozzle comprising a tip and having an outer periphery; a mold secured to said hot runner and including: a mold cavity; and a nozzle-receiving cavity in fluid communication with said mold cavity and receiving a portion of said injection nozzle, said nozzle-receiving cavity including a sealing surface and a tip region receiving said tip of said injection nozzle; and a nozzle sleeve surrounding said outer periphery of at least a portion of said injection nozzle and secured to the injection molding apparatus independently of said injection nozzle, said nozzle sleeve including a nozzle sealing opening receiving a portion of said injection nozzle therethrough and configured to form a seal with said injection nozzle at least when said injection nozzle and said nozzle sleeve are at an operating temperature, said nozzle sleeve springingly urged between said hot runner and said sealing surface so as to seal said tip region relative to said nozzle-receiving cavity.
 2. The injection molding assembly of claim 1, wherein said nozzle sleeve is secured to said hot runner so that said nozzle sleeve is retained on said hot runner when said mold is disengaged from said hot runner.
 3. The injection molding assembly of claim 2, wherein said injection nozzle has a longitudinal central axis and said nozzle sleeve is movably secured to said hot runner so as to be movable substantially only in a direction parallel to said longitudinal central axis.
 4. The injection molding assembly of claim 3, wherein said hot runner further includes a retainer and an urging means urging said nozzle sleeve against said sealing surface and, when said mold is not engaged with said hot runner, for urging said nozzle sleeve toward said retainer.
 5. The injection molding assembly of claim 4, wherein said urging means is formed integrally with said nozzle sleeve.
 6. The injection molding assembly of claim 4, wherein said urging means is formed separately from said nozzle sleeve.
 7. The injection molding assembly of claim 1, wherein said nozzle sleeve is secured to said mold independent from said injection nozzle so that said nozzle sleeve is retained on said mold when said mold is disengaged from said hot runner.
 8. The injection molding assembly of claim 7, wherein said injection nozzle has a longitudinal central axis and said nozzle sleeve is movably secured to said mold so as to be movable substantially only in a direction parallel to said longitudinal central axis.
 9. The injection molding assembly of claim 8, wherein said mold further includes a retainer and an urging means urging said nozzle sleeve between said hot runner and said sealing surface and, when said mold is not engaged with said hot runner, for urging said nozzle sleeve toward said retainer.
 10. The injection molding assembly of claim 9, wherein said urging means is formed integrally with said nozzle sleeve.
 11. The injection molding assembly of claim 10, wherein a portion of said urging means defines said nozzle sealing opening.
 12. The injection molding assembly of claim 11, wherein said urging means is compressed into sealing engagement with said injection nozzle.
 13. The injection molding assembly of claim 1, wherein said hot runner further includes an urging means urging said nozzle sleeve against said sealing surface.
 14. The injection molding assembly of claim 13, wherein said urging means is formed integrally with said nozzle sleeve proximate said hot runner.
 15. The injection molding assembly of claim 13, wherein said urging means is formed separately from said nozzle sleeve.
 16. The injection molding assembly of claim 13, wherein said urging means is formed integrally with said nozzle sleeve proximate said mold.
 17. The injection molding assembly of claim 16, wherein a portion of said urging means defines said nozzle sealing opening.
 18. The injection molding assembly of claim 17, wherein said urging means is compressed into sealing engagement with said injection nozzle.
 19. The injection molding assembly of claim 1, wherein said sealing surface is tapered so as to assist in aligning said mold and said hot runner with one another when engaging said mold to said hot runner.
 20. An injection mold for use with a hot runner that has a mold-confronting face and includes at least one nozzle proximate the mold-confronting face, the injection mold comprising: a nozzle-sleeve receiver; a nozzle sleeve including a nozzle-sealing opening for receiving the at least one nozzle when the hot runner is properly engaged with the injection mold; and a nozzle-sleeve retainer movably securing said nozzle sleeve to the injection mold; wherein said nozzle sleeve is springingly biased into engagement with said nozzle-sleeve retainer when the injection mold is distal from the hot runner and said nozzle sleeve is springingly biased into sealing engagement with said nozzle-sleeve receiver when the mold is properly engaged with the hot runner.
 21. The mold of claim 20, further comprising an urging means springingly urging said nozzle sleeve into engagement with said nozzle-sleeve retainer when the mold is distal from the hot runner and springingly urging said nozzle sleeve into sealing engagement with the nozzle-sleeve receiver when the mold is properly engaged with the hot runner.
 22. The mold of claim 21, wherein said urging means is formed integrally with said nozzle sleeve.
 23. The mold of claim 20, wherein said nozzle sleeve is configured to seal with the at least one nozzle as the mold is moved into proper engagement with the hot runner. 